Conventional dental vacuum systems require periodic, and frequently expensive, upkeep. Such upkeep may involve replacement and maintenance of motors required to produce the requisite vacuum for the dental operatories being serviced. Conventional wet system dental vacuums normally use a single large, powerful motor, or two such large motors mounted in parallel arrangements. When large motors of a turbine type are used, e.g., in parallel arrangements, such arrangements are normally for use in large dental offices and are quite expensive due primarily to the cost of such motors. In contrast, so-called dry systems typically generate vacuum with high speed vane type fans, and their operating motors are smaller and usually much noisier and shorter lived than conventional water sealed impeller type pumps used in wet systems. An air series arrangement in such dry systems, while known, is not widely adopted because an air exhaust from a first unit, e.g., serving to supply inlet air to a second unit causes that second unit to quickly heat up. This heat frequently results in premature motor failure within an unacceptably short period of time, particularly with small, inexpensive motors used for power operation of vacuum creating blowers.